Potts examines the development of nomadism in Iran over the course of three millennia. Evidence of nomadism in prehistory is examined and found insufficient to justify claims of its great antiquity. The background of the earliest nomadic groups, identified as Persian tribes by Herodotus, is examined within the context of the migration of Iranian speakers onto the Iranian plateau in the late second or early first millennium B.C. Thereafter, evidence of nomadic groups in Late Antiquity and early Islamic times is reviewed.